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Stenoplesictis

Stenoplesictis is an extinct genus of enigmatic aeluroid carnivoran restricted to western Europe that lived during the Oligocene epoch. It was named by Henri Filhol in 1880 and contains the type species S. cayluxi as well as two other species, S. minor and S. crocheti. While several additional species from Asia and Africa had been assigned to it, S. muhoronii is the only species of Stenoplesictis needing a reassignment to another genus.

Taxonomy
In 1880, the French palaeontologist Henri Filhol described a maxilla from the French lime phosphate deposits of Caylux, considering it as an unknown mustelid genus. He wrote that the premolars were similar to those of Proailurus but differed by not being as large. Filhol also recorded that the mandible had 3 incisors, 1 canine, 4 premolars, and 2 molars. He erected the genus name Stenoplesictis, referencing it after the fossil mustelid genus Plesictis and creating the species name Stenoplesictis cayluxi. The etymology is derived from στενός (Ancient Greek for "narrow") and the genus name Plesictis, which itself means "near weasel" in Ancient Greek. In 1882, in addition to reaffirming the validity of S. cayluxi, described as small-sized in relation to other carnivorans, he went on to name a smaller-sized species S. minor based on several lower jaws with incomplete dental sets. In 1924, the Americans palaeontologists William Diller Matthew and Walter W. Granger erected Cynodictis? elegans based on lower dentition from the Hsanda Gol Formation of Mongolia, noting that the genus placement is tentative because of the lack of molars. In 1987, German palaeontologist Norbert Schmidt-Kittler erected S. muhoronii based on a maxilla fragment, deriving it from the Kenyan town of Muhoroni near where the type locality of Songhor was found. C? elegans was reclassified to Stenoplesictis as S. elegans by Demberelyin Dashzeveg in 1996, who also erected S. indigenus based on a lower jaw fragment from the eastern Gobi Desert in Mongolia and S. simplex based on a fragmented lower jaw from the Ergilin Dzo Formation. In 1999, French palaeontologists Stéphane Peigné and Louis de Bonis made S. minor a synonym of S. cayluxi, arguing that the purported differences between the two species are too minor to justify separation. They also created the species S. crocheti, stating that it is a species known from cranial evidence from France that was named after J.-Y Crochet, who discovered the Pech du Fraysse locality in 1971. Additionally, they wrote that S. muhoronii, S. indigenus, S. simplex, and S. elegans did not belong to Stenoplesictis, meaning that they needed to be assigned to other genera. "S." muhoronii being a species pending reassignment was followed by Michael Morlo et al. (or "and colleagues") in 2007. In 2015, Naoko Egi et al. erected the genus Alagtsavbaatar, reassigning "S." indigenus to it as A. indigenus. They also made S. simplex a synonym of A. gracilis, previously classified in Palaeoprionodon. S. minor as a species was revived by de Bonis et al. in 2022 when they described a cranium that they assigned to it. "Cynodictis" elegans is not considered to be a species of Stenoplesictis and is also currently pending a reassignment to another genus. The origins of the Feliformia can be traced back from the Middle Eocene, with various families diverging from the Late Eocene to the Oligocene. The Stenoplesictidae is very poorly known but has been recorded from the Oligocene of Eurasia and Miocene of Africa. Stenoplesictictis was among the stenoplesictid genera that was known exclusively from Europe during the Oligocene. According to Peigné and de Bonis, Stenoplesictis is a primitive genus of feliform but is slightly more derived (or evolutionarily recent) than the extant African palm civet (Nandinia binotata). == Description ==
Description
Skull Stenoplesictis differs from other genera in having a flattened upper face of the skull. Its snout is not as narrow as that of another stenoplesictid Haplogale. In terms of addition diagnoses, the lateral (or sideway) edge of the basicranium projects and is in contact with the auditory bulla. Its auditory region is differentiated from Palaeoprionodon by its larger ectotympanic and non-ossified entotympanic that is positioned back and from Stenogale by the lack of any anteroposterior flattened underside process (or tissue projection) on the promontory of the tympanic cavity. In the auditory region of S. cayluxi, the elongated auditory bulla consists of the ectotympanic, rostral entotympanic, and caudal entotympanic bones. The promontory of the tympanic cavity is larger than that of the African palm civet, is particularly proportionally large in its underside, and is centered within the middle ear cavity's anteroposterior area. The oval window is round and opens to the middle ear cavity's ectotympanic area. The mastoid process is narrow compared to that of the African calm civet. The ear canal appears oval and lacks any meatal fossa, a depression within the ear's inner region. The rhinal sulci have low positions relative to the brain, which suggests that the paleocortex is reduced compared to the neocortex. The olfactory bulbs are pear-shaped, project forward, and are relatively developed, consisting of 3% of the known endocast's brain volume. The cerebrum makes up a considerable portion of the brain's length within a sagittal plane. The coronolateral sulcus appears straight while the suprasylvian sulcus (or suprasylvia) has a slight arch. The cerebellum in comparison occupies a quarter of the brain's total length and makes up for 28% of the endocast's volume. == Palaeoecology ==
Palaeoecology
Early Oligocene Although the Eocene-Oligocene transition marked long-term drastic cooling global climates, western Eurasia was still dominated by humid climates, albeit with dry winter seasons in the Oligocene. Europe during the Oligocene had environments largely adapted to winter-dry seasons and humid seasons that were composed of three separate vegetational belts by latitude, with temperate needleleaf-broadleaved or purely broadleaved deciduous forests aligning with the northernmost belt between 40°N and 50°N, the middle belt of warmth-adapted mixed mesophytic and evergreen broadleaved forests aligning between 40°N and 30°N, and the last belt containing tropical vegetation aligning below 30°N. Feliforms, represented by the Nimravidae and Aeluroidea, both make their appearances in western Europe at MP21 after the Grande Coupure extinction and faunal turnover event. S. cayluxi extends in temporal range up to MP28, which dates to the Late Oligocene and records a short temporal appearance of S. crocheti. Pech du Fraysse, which dates to MP28 and has known fossil evidence of both S. cayluxi and S. crocheti, also records those of the herpetotheriids Amphiperatherium and Peratherium, talpids Geotrypus and Mygatalpa, theridomyids Issiodoromys and Archaeomys, eomyid Eomys, cricetids Eucricetodon and Pseudocricetodon, glirid Gliravus, hyaenodontid Hyaenodon, ursid Cephalogale, ailurid Amphictis, cainotheres Plesiomeryx and Caenomeryx, suoid Palaeochoerus, and the ruminant Dremotherium. == References ==
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